Metal plate

ABSTRACT

The object of the present invention is to provide a metal plate capable of manufacturing a deposition mask in which dispersion of positions of through-holes is restrained. A thermal recovery rate is defined as parts per million of a difference a distance between to measurement points on a sample before a heat treatment and a distance therebetween after the heat treatment, relative to the distance therebetween before the heat treatment. In this case, an average value of the thermal recovery rates of the respective samples is not less than −10 ppm and not more than +10 ppm, and (2) a dispersion of the thermal recovery rates of the respective samples is not more than 20 ppm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/703,101, filed Sep. 13, 2017, which is a continuation of U.S.application Ser. No. 15/026,009, filed Mar. 30, 2016, now U.S. Pat. No.9,828,665, issued Nov. 28, 2017, which in turn is the National Stageentry of International Application No. PCT/JP2014/075168, filed Sep. 24,2014, the entireties of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a metal plate for use in manufacturinga deposition mask with a plurality of through-holes formed therein. Inaddition, the present invention relates to a method of manufacturing themetal plate. In addition, the present invention relates to a method ofmanufacturing the mask with a plurality of through-holes formed therein,by use of the metal plate.

BACKGROUND OF THE INVENTION

A display device used in a portable device such as a smart phone and atablet PC is required to have high fineness, e.g., an image density notless than 300 ppi. In addition, there is increasing demand that theportable device is applicable in the full high-definitions standard. Inthis case, the image density of the display device needs to be 450 ppior more.

An organic EL display device draws attention because of its excellentresponsibility and low power consumption. A known method of formingpixels of an organic EL display device is a method which uses adeposition mask including through-holes that are arranged in a desiredpattern, and forms pixels in the desired pattern. To be specific, adeposition mask is firstly brought into tight contact with a substratefor organic EL display device, and then the substrate and the depositionmask in tight contact therewith are put into a deposition apparatus soas to deposit an organic material and so on. In general, a depositionmask can be manufactured by forming through-holes in a metal plate bymeans of an etching process using photolithographic technique (forexample, Patent Document 1). For example, a resist film is firstlyformed on the metal plate. Then, the resist film, with which an exposuremask is in tight contact, is exposed to form a resist pattern.Thereafter, through-holes are formed by etching areas of the metalplate, which are not covered with the resist pattern.

Patent Document 1: JP2004-039319A

SUMMARY OF THE INVENTION

When a film of a deposition material is formed on a substrate with theuse of a deposition mask, the deposition material adheres not only tothe substrate but also to the deposition mask. For example, some of thedeposition material moves toward the substrate along a direction largelyinclined with respect to a normal direction of the deposition mask. Sucha deposition material reaches a wall surface of a through-hole of thedeposition mask and adheres thereto, before it reaches the substrate. Inthis case, the deposition material is not likely to adhere to an area ofthe substrate, which is located near the wall surface of thethrough-hole of the deposition mask, so that a thickness of thedeposition material adhered to this area may be smaller than a thicknessof another part and/or there may be a part to which no depositionmaterial adheres. Namely, the deposition near the wall surface of thethrough-hole of the deposition mask may become unstable. Thus, when thisdeposition mask is used for forming pixels of an organic EL displaydevice, dimensional precision of each pixel and positional precisionthereof lower, which lowers luminous efficiency of the organic ELdisplay device.

One of possible solutions to this problem is to reduce a thickness of ametal plate used for manufacturing a deposition mask. This is because,since the thickness of the metal plate is reduced, a height of a wallsurface of a through-hole of a deposition mask can be reduced, whereby arate of a deposition material, which adheres to the wall surface of thethrough-hole, can be lowered. However, in order to obtain a metal platewith a reduced thickness, it is necessary to increase a reduction ratioupon manufacture of the metal plate by rolling a base metal. Thereduction ratio herein means a value obtained by a calculation of(thickness of base metal minus thickness of metal plate)/(thickness ofbase metal). When a metal is rolled, strain occurs in the rolled metal.Even if the metal is heat-treated such as annealed after being rolled,it is not easy to completely remove the strain for a short period oftime. Thus, a metal plate used for manufacturing a deposition maskgenerally has a strain that remains inside the metal plate, i.e., aremaining strain.

A step using a metal plate to manufacture a deposition mask and adeposition step using the deposition mask respectively include a step ofapplying heat to the metal plate constituting the deposition mask. Atthis time, because of the heat, there is a possibility that a remainingstress in the metal plate is removed and/or that a crystallineorientation changes. When the remaining stress is removed and/or thecrystalline orientation changes, the dimension of the metal plate mayreduce. For example, when the remaining stress is removed, since thematerial shape held by the remaining stress changes such that there isno strain as much as possible, the dimension of the metal plate mayreduce. On the other hand, when the crystalline orientation changes, thecrystalline density changes to higher the density, the dimension of themetal plate may reduce.

The fact that the dimension of the metal plate constituting a depositionmask may change means that positions of through-holes formed in thedeposition mask may change by means of heat. In addition, there is apossibility that the degree of remaining strain inside the metal platechanges in the width direction of the metal plate. In this case, thedegree at which the positions of the through-holes change by heatdiffers depending on a position in the width direction of the originalelongated metal plate where the metal plate constituting the depositionmask occupies. This means not only that the positions of thethrough-holes formed in the deposition mask change by heat, but alsothat the degree of change differs in each individual deposition mask.Thus, in order to precisely set the positions of the through-holes ineach deposition mask, it is important to use, as an original elongatedmetal plate, an elongated metal plate having a small remaining straindegree and its dispersion. Such a problem is not recognized in the abovePatent Document 1.

The present invention has been made in view of the above circumstances.The object of the present invention is to provide a metal plate used formanufacturing a deposition mask having through-holes that are formedwith high positioning precision. In addition, the object of the presentinvention is to provide a method of manufacturing a metal plate and amethod of manufacturing a mask.

The present invention is a method of manufacturing a metal plate to beused for manufacturing a deposition mask by forming a plurality ofthrough-holes in the metal plate, the method comprising:

-   -   a rolling step of rolling a base metal to obtain the metal        plate; and    -   an annealing step of annealing the metal plate obtained by the        rolling step;    -   wherein:    -   the through-holes of the deposition mask are formed by etching        the elongated metal plate,    -   when a plurality of samples are taken out from the metal plate,        a distance between two measurement points on each sample, which        is measured before a heat treatment, is referred to as L1, a        distance therebetween which is measured after the heat treatment        is referred to as L2, and a thermal recovery rate F of each        sample is defined by the following expression:        F={(L1−L2)/L1}×10⁶ (ppm), the following conditions (1) and (2)        are satisfied:        -   (1) an average value of the thermal recovery rates of the            respective samples is not less than −10 ppm and not more            than +10 ppm; and        -   (2) a dispersion of the thermal recovery rates of the            respective samples is not more than 20 ppm;    -   the samples are obtained by cutting at least one sample metal        plate, which is obtained by cutting the metal plate along a        width direction of the metal plate, into two or more along a        longitudinal direction of the metal plate;    -   the two measurement points on the sample are aligned along the        longitudinal direction of the metal plate;    -   the heat treatment includes a first step of increasing a        temperature of each sample from 25° C. to 300° C. for 30        minutes, a second step of keeping the temperature of each sample        at 300° C. for 5 minutes, and a third step of decreasing the        temperature of each sample from 300° C. to 25° C. for 60        minutes; and    -   the dispersion of the thermal recovery rates is a value obtained        by multiplying 3 to a standard deviation of the thermal recovery        rates of the respective samples.

In the method of manufacturing a metal plate, the annealing step may beperformed while pulling the rolled base metal in the longitudinaldirection. Alternatively, the annealing step may be performed to themetal plate wound around a core.

In the method of manufacturing a metal plate, the base metal may includean invar alloy.

The present invention is a metal plate to be used for manufacturing adeposition mask by forming a plurality of through-holes in the metalplate,

-   -   wherein:    -   the through-holes of the deposition mask are formed by etching        the elongated metal plate,    -   when a plurality of samples are taken out from the metal plate,        a distance between two measurement points on each sample, which        is measured before a heat treatment, is referred to as L1, a        distance therebetween which is measured after the heat treatment        is referred to as L2, and a thermal recovery rate F of each        sample is defined by the following expression:        F={(L1−L2)/L1}×10⁶ (ppm), the following conditions (1) and (2)        are satisfied:        -   (1) an average value of the thermal recovery rates of the            respective samples is not less than −10 ppm and not more            than +10 ppm; and        -   (2) a dispersion of the thermal recovery rates of the            respective samples is not more than 20 ppm;    -   the samples are obtained by cutting at least one sample metal        plate, which is obtained by cutting the metal plate along a        width direction of the metal plate, into two or more along a        longitudinal direction of the metal plate;    -   the two measurement points on the sample are aligned along the        longitudinal direction of the metal plate;    -   the heat treatment includes a first step of increasing a        temperature of each sample from 25° C. to 300° C. for 30        minutes, a second step of keeping the temperature of each sample        at 300° C. for 5 minutes, and a third step of decreasing the        temperature of each sample from 300° C. to 25° C. for 60        minutes; and    -   the dispersion of the thermal recovery rates is a value obtained        by multiplying 3 to a standard deviation of the thermal recovery        rates of the respective samples.

The metal plate according to the present invention may include an invaralloy.

The present invention is a method of manufacturing a deposition maskhaving a plurality of through-holes formed therein, comprising:

-   -   a step of preparing a metal plate;    -   a resist pattern forming step of forming a resist pattern on the        metal plate; and    -   an etching step of etching an area of the metal plate, which is        not covered with the resist pattern, to form recesses in the        metal plate, the recesses being configured to define the        through-holes;    -   wherein:    -   when a plurality of samples are taken out from the metal plate,        a distance between two measurement points on each sample, which        is measured before a heat treatment, is referred to as L1, a        distance therebetween which is measured after the heat treatment        is referred to as L2, and a thermal recovery rate F of each        sample is defined by the following expression:        F={(L1−L2)/L1}×10⁶ (ppm), the following conditions (1) and (2)        are satisfied:        -   (1) an average value of the thermal recovery rates of the            respective samples is not less than −10 ppm and not more            than +10 ppm; and        -   (2) a dispersion of the thermal recovery rates of the            respective samples is not more than 20 ppm;    -   the samples are obtained by cutting at least one sample metal        plate, which is obtained by cutting the metal plate along a        width direction of the metal plate, into two or more along a        longitudinal direction of the metal plate;    -   the two measurement points on the sample are aligned along the        longitudinal direction of the metal plate;    -   the heat treatment includes a first step of increasing a        temperature of each sample from 25° C. to 300° C. for 30        minutes, a second step of keeping the temperature of each sample        at 300° C. for 5 minutes, and a third step of decreasing the        temperature of each sample from 300° C. to 25° C. for 60        minutes; and    -   the dispersion of the thermal recovery rates is a value obtained        by multiplying 3 to a standard deviation of the thermal recovery        rates of the respective samples.

In the method of manufacturing a deposition mask according to thepresent invention, the resist-pattern forming step may include:

-   -   a step of forming a resist film on the metal plate;    -   a step of bringing an exposure mask into vacuum contact with the        resist film;    -   a step of exposing the resist film in a predetermined pattern        through the exposure mask; and    -   a developing step of forming an image on the exposed resist        film;    -   wherein the developing step includes a resist heat treatment        step of increasing a hardness of the resist film.

In the method of manufacturing a deposition mask according to thepresent invention, the metal plate may include an invar alloy.

According to the present invention, a deposition mask having arestrained dispersion of positions of through-holes can be obtained.Thus, positioning precision of a deposition material adhered to asubstrate can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for explaining an embodiment of the present invention,which is a schematic plan view showing an example of a deposition maskapparatus including deposition masks.

FIG. 2 is a view for explaining a deposition method by use of thedeposition mask apparatus shown in FIG. 1.

FIG. 3 is a partial plan view showing the deposition mask shown in FIG.1.

FIG. 4 is a sectional view taken along the line IV-IV of FIG. 3.

FIG. 5 is a sectional view taken along the line V-V of FIG. 3.

FIG. 6 is a sectional view taken along the line VI-VI of FIG. 3.

FIG. 7A is a view showing a step of rolling a base metal to obtain ametal plate having a desired thickness.

FIG. 7B is a view showing a step of annealing the metal plate obtainedby the rolling operation.

FIG. 8A is a plan view showing an elongated metal plate.

FIG. 8B is a plan view showing sample metal plates cut out from theelongated metal plate.

FIG. 8C is a plan view showing samples cut out from the sample metalplates.

FIG. 9A is a view showing a heat treatment applied to the sample.

FIG. 9B (a) is a plan view showing the sample before it is subjected tothe heat treatment.

FIG. 9B (b) is a plan view showing the sample after it is subjected tothe heat treatment.

FIG. 10 is a diagrammatic view for generally explaining an example of amethod of manufacturing a deposition mask shown in FIG. 1.

FIG. 11 is a view for explaining an example of the method ofmanufacturing a deposition mask, which is a sectional view showing astep of forming a resist film on a metal plate.

FIG. 12 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a sectional view showing astep of bringing an exposure mask into tight contact with the resistfilm.

FIG. 13 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing an elongatedmetal plate in a section along a normal direction.

FIG. 14 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing the elongatedmetal plate in the section along the normal direction.

FIG. 15 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing the elongatedmetal plate in the section along the normal direction.

FIG. 16 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing the elongatedmetal plate in the section along the normal direction.

FIG. 17 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing the elongatedmetal plate in the section along the normal direction.

FIG. 18 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing the elongatedmetal plate in the section along the normal direction.

FIG. 19 is a view for explaining the example of the method ofmanufacturing a deposition mask, which is a view showing the elongatedmetal plate in the section along the normal direction.

FIG. 20 is a view showing a modification example of the deposition maskapparatus including deposition masks.

FIG. 21 is a view showing measurement results of thermal recovery ratesof first to tenth samples cut from first to tenth winding bodies.

FIG. 22 is a view showing evaluation results of a primary effect indeposition masks manufactured by elongated metal plates obtained fromthe first to the tenth winding bodies.

FIG. 23 is a view showing evaluation results of a secondary effect inthe deposition masks manufactured by the elongated metal plates obtainedfrom the first to tenth winding bodies.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described herebelow withreference to the drawings. In the drawings attached to thespecification, a scale dimension, an aspect ratio and so on are changedand exaggerated from the actual ones, for the convenience of easiness inillustration and understanding.

FIGS. 1 to 19 are drawings for explaining an embodiment of the presentinvention. In the below embodiment and its modification examples, amethod of manufacturing a deposition mask, which is used for patterningan organic material in a desired pattern on a substrate when an organicEL display device is manufactured, is described by way of example.However, not limited to this application, the present invention can beapplied to a method of manufacturing a deposition mask to be used invarious applications.

In this specification, the terms “plate”, “sheet” and “film” are notdifferentiated from one another based only on the difference of terms.For example, the “plate” is a concept including a member that can bereferred to as sheet or film. Thus, for example, “metal plate” is notdifferentiated from a member that is referred to as “metal sheet” or“metal film” based only on the difference of terms.

In addition, the term “plate plane (sheet plane, film plane)” means aplane corresponding to a plane direction of a plate-like (sheet-like,film-like) member as a target, when the plate-like (sheet-like,film-like) member as a target is seen as a whole in general. A normaldirection used to the plate-like (sheet-like, film-like) member means anormal direction with respect to a plate plane (sheet surface, filmsurface) of the member.

Further, in this specification, terms specifying shapes, geometricconditions and their degrees, e.g., “parallel”, “perpendicular”, “same”,“similar” etc., are not limited to their strict definitions, butconstrued to include a range capable of exerting a similar function.

Deposition Mask Apparatus

Firstly, an example of a deposition mask apparatus including depositionmasks to be manufactured is described with reference mainly to FIGS. 1to 6. FIG. 1 a plan view showing an example of the deposition maskapparatus including the deposition masks. FIG. 2 is a view forexplaining a method of using the deposition mask apparatus shown inFIG. 1. FIG. 3 is a plan view showing the deposition mask seen from afirst surface side. FIGS. 4 to 6 are sectional views seen fromrespective positions of FIG. 3.

The deposition mask apparatus 10 shown in FIGS. 1 and 2 includes aplurality of deposition masks 20 each of which is formed of a metalplate 21 of substantially a rectangular shape, and a frame 15 attachedto peripheries of the deposition masks 20. Each deposition mask 20 has anumber of through-holes 25 formed by etching the metal plate 21, whichhas a first surface 21 a and a second surface 21 b opposed to eachother, at least from the first surface 21 a. As shown in FIG. 2, thedeposition mask apparatus 10 is used for depositing a depositionmaterial to a substrate. The deposition mask apparatus 10 is supportedin a deposition apparatus 90 such that the deposition mask 20 faces alower surface of the substrate such as a glass substrate 92, onto whichthe deposition material is to be deposited.

In the deposition apparatus 90, the deposition mask 20 and the glasssubstrate 92 are brought into tight contact with each other by amagnetic force of magnets, not shown. In the deposition apparatus 90,there are disposed below the deposition mask apparatus 10 a crucible 94storing a deposition material (e.g., organic luminescent material) 98and a heater 96 for heating the crucible 94. The deposition material 98in the crucible 94 is evaporated or sublimated by heat applied from theheater 96 so as to adhere to the surface of the glass substrate 92. Asdescribed above, since the deposition mask 20 has a lot of through-holes25, the deposition material 98 adheres to the glass substrate 92 throughthe through-holes 25. As a result, a film of the deposition material 98is formed on the surface of the glass substrate 92 in a desired patterncorresponding to the positions of the through-holes 25 of the depositionmask 20.

As described above, in this embodiment, the through-holes 25 arearranged in each effective area 22 in a predetermined pattern. When acolor display is desired, an organic luminescent material for red color,an organic luminescent material for green color and an organicluminescent material for blue color may be sequentially deposited, whilethe deposition mask 20 (deposition mask apparatus 10) and the glasssubstrate 92 are relatively moved little by little along the arrangementdirection of the through-holes 25 (aforementioned one direction).

The frame 15 of the deposition mask apparatus 10 is attached to theperipheries of the rectangular deposition masks 20. The frame 15 isconfigured to hold each deposition mask in a tensed state in order toprevent the deposition mask 20 from warping. The deposition masks 20 andthe frame 15 are fixed with respect to each other by spot welding, forexample.

The deposition process is performed inside the deposition apparatus 90in a high-temperature. Thus, during the deposition process, thedeposition masks 20, the frame 15 and the substrate 92, which are heldinside the deposition apparatus 90, are also heated. At this time, eachdeposition mask 20, the frame 15 and the substrate 92 developdimensional change behaviors based on their respective thermal expansioncoefficients. In this case, when the thermal expansion coefficients ofthe deposition mask 20, the frame 15 and the substrate 92 largely differfrom one another, positioning displacement occurs because of thedifference in dimensional change. As a result, the dimensional precisionand the positional precision of the deposition material to be adhered tothe substrate 92 lower. In order to avoid this problem, the thermalexpansion coefficient of the deposition mask 20 and the frame 15 ispreferably equivalent to the thermal expansion coefficient of thesubstrate 92. For example, when a glass substrate 92 is used as thesubstrate 92, an invar alloy, which is an iron alloy obtained by addingto iron a predetermined amount of nickel, e.g., 36% by mass, may be usedas a material of the deposition mask 20 and the frame 15.

Deposition Mask

Next, the deposition mask 20 is described in detail. As shown in FIG. 1,in this embodiment, each deposition mask 20 is formed of the metal plate21, and has an outline of a substantially quadrangular shape in planview, more precisely, a substantially rectangular shape in plan view.The metal plate 21 of the deposition mask 20 includes the effective area22 in which the through-holes 25 are formed in a regular arrangement,and a surrounding area 23 surrounding the effective area 22. Thesurrounding area 23 is an area for supporting the effective area 22, andis not an area through which the deposition material intended to bedeposited on the substrate passes. For example, in the deposition mask20 for use in depositing an organic luminescent material for organic ELdisplay device, the effective area 22 is an area in the deposition mask20, which faces a section on the substrate (glass substrate 92) to whichthe organic luminescent material is deposited to form pixels, i.e., asection on the substrate which provides a display surface of themanufactured substrate for organic EL display device. However, forvarious reasons, the surrounding area 23 may have a through-hole and/ora recess. In the example shown in FIG. 1, each effective area 22 has anoutline of a substantially quadrangular shape in plan view, moreprecisely, a substantially rectangular shape in plan view.

In the illustrated example, the effective areas 22 of the depositionmasks 20 are aligned in line, at predetermined intervals therebetween,along one direction in parallel with a longitudinal direction of thedeposition mask 20. In the illustrated example, one effective area 22corresponds to one organic EL display device. Namely, the depositionmask apparatus 10 (deposition masks 20) shown in FIG. 1 enables amultifaceted deposition.

As shown in FIG. 3, in the illustrate example, a plurality of thethrough-holes 25 formed in each effective area 22 are arranged atpredetermined pitches along two directions perpendicular to each other.An example of the through-hole 25 formed in the metal plate 21 isdescribed in more detail with reference mainly to FIGS. 3 to 6.

As shown in FIGS. 4 to 6, a plurality of the through-holes 25 extendbetween the first surface 20 a, which is one side along a normaldirection of the deposition mask 20, and the second surface 20 b, whichis the other side along the normal direction of the deposition mask 20,to pass through the deposition mask 20. In the illustrated example, asdescribed in more detail later, a first recess 30 is formed in the metalplate 21 by an etching process from the side of the first surface 21 aof the metal plate 21, which is the one side in the normal direction ofthe deposition mask, and a second recess 35 is formed in the metal plate21 from the side of the second surface 21 b, which is the other side inthe normal direction of the metal plate 21. The through-hole 25 iscomposed of the first recess 30 and the second recess 35.

As shown in FIGS. 3 to 6, a cross-sectional area of each first recess30, in a cross section along a plate plane of the deposition mask 20 ateach position along the normal direction of the deposition mask 20,gradually decreases from the side of the first surface 20 a of thedeposition mask 20 toward the side of the second surface 20 b. As shownin FIG. 3, a wall surface 31 of the first recess 30 extends in its allarea in a direction intersecting with the normal direction of thedeposition mask 20, and is exposed to the one side along the normaldirection of the deposition mask 20. Similarly, a cross-sectional areaof each second recess 35, in a cross section along the plate plane ofthe deposition mask 20 at each position along the normal direction ofthe deposition mask 20, may gradually decrease from the side of thesecond surface 20 b of the deposition mask 20 toward the side of thefirst surface 20 a. A wall surface 36 of the second recess 35 extends inits all area in a direction intersecting with the normal direction ofthe deposition mask 20, and is exposed to the other side along thenormal direction of the deposition mask 20.

As shown in FIGS. 4 to 6, the wall surface 31 of the first recess 30 andthe wall surface 36 of the second recess 35 are connected via acircumferential connection portion 41. The connection portion 41 isdefined by a ridge line of a bulging part where the wall surface 31 ofthe first recess 30, which inclined with respect to the normal directionof the deposition mask 20, and the wall surface 36 of the second recess35, which is inclined with respect to the normal direction of thedeposition mask 20, are merged with each other. The connection portion41 defines a through portion 42 where an area of the through-hole 25 isminimum in plan view of the deposition mask 20.

As shown in FIGS. 4 to 6, the two adjacent through-holes 25 in the otherside surface along the normal direction of the deposition mask, i.e., inthe second surface 20 b of the deposition mask 20, are spaced from eachother along the plate plane of the deposition mask. Namely, as in thebelow-described manufacturing method, when the second recesses 35 aremade by etching the metal plate 21 from the side of the second surface21 b of the metal plate 21, which will correspond to the second surface20 b of the deposition mask 20, the second surface 21 b of the metalplate 21 remains between the two adjacent recesses 35.

On the other hand, as shown in FIGS. 4 to 6, the two adjacent firstrecesses 30 are connected to each other on the one side along the normaldirection of the deposition mask, i.e., on the side of the first surface20 a of the deposition mask 20. Namely, as in the below-describedmanufacturing method, when the first recesses 30 are made by etching themetal plate 21 from the side of the first surface 21 a of the metalplate 21, which will correspond to the first surface 20 a of thedeposition mask 20, no first surface 21 a of the metal plate 21 remainsbetween the two adjacent first recesses 30. Namely, the first surface 21a of the metal plate 21 is etched as a whole over the effective area 22.According to the first surface 20 a of the deposition mask 20 formed bythese first recesses 30, when the deposition mask 20 is used such thatthe first surface 20 a of the deposition mask 20 faces the depositionmaterial 98 as shown in FIG. 2, a utilization efficiency of thedeposition material 98 can be effectively improved.

As shown in FIG. 2, the deposition mask apparatus 10 is received in thedeposition apparatus 90. In this case, as shown by the two-dot chainlines in FIG. 4, the first surface 20 a of the deposition mask 20 islocated on the side of the crucible 94 holding the deposition material98, and the second surface 20 b of the deposition mask 20 faces theglass substrate 92. Thus, the deposition material 98 adheres to theglass substrate 92 through the first recess 30 whose cross-sectionalarea gradually decreases. As shown by the arrow in FIG. 4 the depositionmaterial 98 not only moves from the crucible 94 toward the glasssubstrate 92 along the normal direction of the glass substrate 92, butalso sometimes moves along a direction largely inclined with respect tothe normal direction of the glass substrate 92. At this time, when thethickness of the deposition mask 20 is large, most of the diagonallymoving deposition material 98 reaches the wall surface 31 of the firstrecess 30, before the deposition material 98 passes through thethrough-hole 25 to reach the glass substrate 92. In this case, the areaof the glass substrate 92 facing the through-hole 25 has an area wherethe deposition material 98 is likely to reach, and an area where thedeposition material 98 is unlikely to reach. Thus, in order that theutilization efficiency (a film-deposition efficiency: a rate of thedeposition material adhering to the glass substrate 92) of thedeposition material can be enhanced to save the expensive depositionmaterial, and that a film of the expensive deposition material can bestably and uniformly formed in the desired area, it is important toconstitute the deposition mask 20 such that the diagonally movingdeposition material 98 is made to reach the glass substrate 92 as muchas possible. Namely, it is advantageous to sufficiently increase aminimum angle θ1 (see FIG. 4) that is defined by a line L1, whichpasses, in the cross sections of FIGS. 4 to 6 perpendicular to the sheetplane of the deposition mask 20, the connection portion 41 having theminimum cross-sectional area of the through-hole 25 and another givenposition of the wall surface 31 of the first recess 30, with respect tothe normal direction of the deposition mask 20.

One of possible methods of increasing the angle θ1 is that the thicknessof the deposition mask 20 is reduced so that the height of the wallsurface 31 of the first recess 30 and the height of the wall surface 36of the second recess 35 are reduced. Namely, it can be said that themetal plate 21, which has a thickness as small as possible within arange in which the strength of the deposition mask 20 is ensured, ispreferably used as the metal plate 21 constituting the deposition mask20.

As another possible method of increasing the angle θ1 is that theoutline of the first recess 30 is made optimum. For example, accordingto this embodiment, since the wall surfaces 31 of the two adjacent firstrecesses 30 are merged with each other, the angle θ1 is allowed to besignificantly large (see FIG. 4), as compared with a recess that doesnot merge with another recess, whose wall surfaces (outlines) are shownby the dotted lines. A reason therefor is described below.

As described in detail later, the first recess 30 is formed by etchingthe first surface 21 a of the metal plate 21. In general, a wall surfaceof the recess formed by etching has a curved shape projecting toward theerosion direction. Thus, the wall surface 31 of the recess formed byetching is steep in. an area where the etching starts, and is relativelylargely inclined in an area opposed to the area where the etchingstarts, i.e., the at the deepest point of the recess. On the other hand,in the illustrated deposition mask 20, since the wall surfaces 31 of thetwo adjacent first recesses 30 merge on the side where the etchingstarts, an outline of a portion 43 where distal edges 32 of the wallsurfaces 31 of the two first recesses 30 are merged with each other hasa chamfered shape instead of a steep shape. Thus, the wall surface 31 ofthe first recess 30 forming a large part of the through-hole 25 can beeffectively inclined with respect to the normal direction of thedeposition mask. That is to say, the angle θ1 can be made large.

According to the deposition mask 20 in the present invention, theinclination angle θ1 formed by the wall surface 31 of the first recess30 with respect to the normal direction of the deposition mask can beeffectively increased, in the whole effective area 22. Thus, thedeposition in a desired pattern can be precisely and stably performed,while the utilization efficiency of the deposition material 98 can beeffectively improved.

Material

A material (metal plate) for constituting the above-described depositionmask 20 is described below. In order to obtain the deposition mask 20having a reduced thickness, it is necessary to increase a reductionratio when a metal plate is manufactured by rolling a base plate.However, the larger the reduction ratio is, the larger a stressremaining inside the metal plate, i.e., a remaining stress becomes. Amethod of heating the metal plate is known as a method for removing sucha remaining stress. When the remaining stress is removed by the heatingoperation, there is a possibility that the dimension of the outline themetal plate changes. For example, the dimension in the longitudinaldirection of the metal plate may reduce after the heating of the metalplate. This is because the removal of the remaining stress inside themetal plate invites removal of the remaining strain, and/or the changeof crystalline orientation invites change of the crystalline density. Inthe below description, the phenomenon in which the dimension of theoutline of the metal plate changes because of heat is also referred toas “thermal recovery”.

A step of manufacturing the deposition masks 20 by use of a metal plateincludes a step of applying heat to the metal plate. For example, in astep of forming a resist film on a metal plate, a coating liquidcontaining a negative-type photosensitive resist material is firstlyapplied to the metal plate, and then the coating liquid is dried byheat. At this time, since the heat is applied to the metal plate, theremaining strain may be possibly removed. In addition, in a step ofdeveloping the resist film, the resist film is sometimes heated so as toincrease a hardness of the resist film. Also at this time, since heat isapplied to the metal plate, the remaining strain may be possiblyremoved. Thus, in the manufacturing process of a deposition mask, theaforementioned thermal recovery of the metal plate might occur. Inaddition, in a deposition step using the deposition mask 20,predetermined heat is applied to the deposition mask 20, so that thethermal recovery might occur.

When the removal of remaining strain because of heat uniformly occursirrespective of a position on the metal plate 21, the thermal recoveryof the metal plate 21 also uniformly occurs irrespective of a positionon the metal plate 21. Namely, a change ratio (contraction ratio) of adistance between two given target points on the metal plate 21 is thesame irrespective of the target point positions. On the other hand, whenthe removal of remaining strain because of heat non-uniformly occursdepending on a position on the metal plate 21, the thermal recovery ofthe metal plate 21 also non-uniformly occurs depending on a position onthe metal plate 21. Namely, a change ratio (contraction ratio) of adistance between two given target points on the metal plate 21 differsdepending on the target point positions on the metal plate 21. In thebelow description, the thermal recovery that uniformly occursirrespectively of a position is referred to as “uniform thermalrecovery”, while the thermal recovery that non-uniformly occursdepending on a position is referred to as “non-uniform thermalrecovery”.

Problems that can be caused by the “non-uniform thermal recovery” of themetal plate are studied below.

As shown in FIG. 1, in the deposition step using the deposition mask 20,a plurality of the deposition masks 20 are attached to the frame 15.Each deposition mask 20 is held by the frame 15 in a tensed state. Thus,when the thermal recovery of the metal plate 21 in the longitudinaldirection uniformly occurs irrespective of a position in the widthdirection, the length of the deposition mask 20 with respect to theframe 15 upon attachment can be adjusted by adjusting a tensing amount.Namely, the positions of the through-holes 25 in the deposition mask 20with respect to the frame 15 can be ideally adjusted.

On the other hand, when the thermal recovery of the metal plate 21 inthe longitudinal direction non-uniformly occurs in the width direction,the positions of the through-holes 25 in each deposition mask 20 withrespect to the frame 15 cannot be ideally adjusted even by uniformlytensing a plurality of the deposition masks 20. In addition, adifference between the thermal recovery degrees of the metal plate 21 inthe respective deposition masks 20 is so small that the differencecannot be visually confirmed. Thus, it is difficult to ideally adjustthe positions of the through-holes 25 of the respective deposition masks20 with respect to the frame 15 by independently adjusting the tensingamounts of the respective deposition masks 20. Thus, when the thermalrecovery of the metal plate 21 in the longitudinal directionnon-uniformly occurs in the width direction, positions of light emittinglayers of organic EL display devices, which are manufactured by thedeposition step using the deposition masks 20, vary depending ondispersion of degrees of thermal recovery that occurred in thedeposition masks 20. This invites the dispersion of quality of theorganic EL display devices.

Under these circumstances, it is important to select and use a metalplate having a small dispersion of thermal recovery amounts in the widthdirection. As described above, the thermal recovery in the manufacturingprocess of the deposition masks 20 is caused by the remaining straininside the used metal plate. Thus, the use of a metal plate having asmall dispersion of thermal recovery amounts in the width directioncorresponds to the use of a metal plate having a small dispersion ofremaining strain amounts in the width direction.

Next, an operation and an effect of this embodiment as structured aboveare described. Here, a method of manufacturing a metal plate for use inmanufacturing a deposition mask firstly. Then, a method of manufacturinga deposition mask by use of the obtained metal plate is described.Thereafter, a method of depositing a deposition material onto asubstrate by use of the obtained deposition mask.

Method of Manufacturing Metal Plate

A method of manufacturing a metal plate is firstly described withreference to FIGS. 7A, 7B, FIGS. 8A, 8B, 8C, FIGS. 9A, 9B (a) and 9B(b). FIG. 7A is a view showing a step of obtaining a metal plate havinga desired thickness. FIG. 7B is a view showing a step of annealing themetal plate obtained by the rolling process.

Rolling Step

As shown in FIG. 7A, a base metal 55 formed of an invar alloy isprepared, and the base metal 55 is transported toward a rollingapparatus 56 including a pair of reduction rolls 56 a and 56 b along atransport direction shown by the arrow D1. The base metal 55 havingreached between the pair of reduction rolls 56 a and 56 b is rolled bythe pair of reduction rolls 56 a and 56 b. Thus, a thickness of the basemetal 55 is reduced and is elongated along the transport direction. As aresult, an elongated metal plate 64 having a thickness t₀ can beobtained. As shown in FIG. 7A, a winding body 62 may be formed bywinding up the elongated metal plate 64 around a core 61. Although avalue of the thickness t₀ is not particularly limited, the value is notless than 0.020 mm and not more than 0.100 mm, for example.

FIG. 7A merely shows the rolling step schematically, and a concretestructure and procedure for performing the rolling step are notspecifically limited. For example, the rolling step may include a hotrolling step in which the base metal is processed at a temperature notless than a temperature at which a crystalline orientation of the invaralloy constituting the base metal 55 is changed, and a cold rolling stepin which the base metal 55 is processed at a temperature not more than atemperature at which the crystalline orientation of the invar alloy ischanged.

Slitting Step

After that, there may be performed a slitting step for slitting bothends of the elongated metal plate 64, which is obtained by the rollingstep, in the width direction thereof, over a range of not less than 3 mmand not more than 5 mm. The slitting step is performed to remove a crackthat may be generated on both ends of the elongated metal plate 64because of the rolling step. Due to the slitting step, it can beprevented that a breakage phenomenon of the elongated metal plate 64,which is so-called plate incision, occurs from the crack as a startingpoint.

Annealing Step

After that, in order to remove a remaining stress accumulated by therolling process in the elongated metal plate 64, as shown in FIG. 7B,the elongated metal plate 64 is annealed by using an annealing apparatus57. As shown in FIG. 7B, the annealing step may be performed while theelongated metal plate 64 is being pulled in the transport direction(longitudinal direction). Namely, the annealing step may be performed asa continuous annealing process while the elongated metal plate is beingtransported, instead of a batch-type annealing process. A duration ofthe annealing step is suitably set depending on a thickness of theelongated metal plate 64 and a reduction ratio thereof. For example, theannealing step is performed at 500° C. for 60 seconds. The above “60seconds” mean that it takes 60 seconds for the elongated metal plate 64to pass through a space, which is heated at 500° C., in the annealingapparatus 57.

Due to the annealing step, it is possible to obtain the elongated metalplate 64 of a thickness t₀, from which the remaining strain is removedto a certain extent. The thickness t₀ is generally equal to a maximumthickness Tb in the surrounding area 23 of the deposition mask 20.

The elongated metal plate 64 having the thickness t₀ may be made byrepeating the above rolling step, the slitting step and the annealingstep plural times. FIG. 7B shows the example in which the annealing stepis performed while the elongated metal plate 64 is being pulled in thelongitudinal direction. However, not limited thereto, the annealing stepmay be performed to the elongated metal plate 64 that is wound aroundthe core 61. Namely, the batch-type annealing process may be performed.When the annealing step is performed while the elongated metal plate 64is wound around the core 61, the elongated metal plate 64 may have awarping tendency corresponding to a winding diameter of the winding body62. Thus, depending on a winding diameter of the winding body 62 and/ora material forming the base metal 55, it is advantageous to perform theannealing step while the elongated metal plate 64 is being pulled in thelongitudinal direction.

The aforementioned continuous annealing process is advantageous in thata throughput of the step can be improved as compared with the batch-typeannealing process, but is disadvantageous in that the remaining strainis insufficiently removed as compared with the batch-type annealingprocess. Namely, the above-described thermal recovery is more likely tooccur when the continuous annealing process is performed rather thanwhen the batch-type annealing process is performed.

Cutting Step

After that, there is performed a cutting step of cutting off both endsof the elongated metal plate 64 in the width direction thereof over apredetermined range, so as to adjust the width of the elongated metalplate 64 into a desired width. Thus, the elongated metal plate 64 havinga desired thickness and a desired width can be obtained.

Inspection Step

After that, there is performed an inspection step in which a sample,which was taken out from the obtained elongated metal plate 64, isinspected before and after a heat treatment to know a thermal recoverydegree. FIG. 8A is a plan view showing the obtained elongated metalplate 64. In FIG. 8A, a forward end of the elongated metal plate 64 inthe longitudinal direction is shown by the symbol 64 c, and a rearwardend thereof is shown by the symbol 64 d. In the inspection step, theelongated metal plate 64 is firstly cut along the width direction of theelongated metal plate 64, so that a sample metal plate 75 having apredetermined length in the longitudinal direction is obtained. At leastone sample metal plate 75 is cut out from the elongated metal plate 64constituting one winding body 62. As shown by the dotted lines in FIG.8A, two sample metal plates 75 are cut out in the forward end 64 c ofthe elongated metal plate 64, and two sample plates 75 are cut out inthe rearward end 64 d of the elongated metal plate 64. FIG. 8B showsfour sample metal plates 75 cut out from one elongated metal plate 64.

Then, each sample metal plate 75 is cut in the longitudinal direction ofthe metal plate to obtain a plurality of samples 76. For example, asshown by the dotted lines in FIG. 8B, each sample metal plate 75 isdivided equally into ten in the width direction. FIG. 8C shows fortysamples 76 in total, which are cut out from the four sample metal plates75.

Thereafter, before and after the sample 76 is subjected to a heattreatment, a distance between two measurement points 76 a on each sample76 is measured at a temperature of 25° C. As shown in FIG. 9A, the heattreatment includes a first step S1 of increasing a temperature of eachsample 76 from P1 to P2 for a period of time Z1, a second step S2 ofkeeping the temperature of each sample 76 at P2 for a period of time Z2,and a third step S3 of decreasing the temperature of each sample 76 fromP2 to P1 for a period of time Z3. The periods of time Z1, Z2, Z3 and thetemperatures P1 and P2 are set to simulate heat to be applied to themetal plate 21 in the manufacturing process of the deposition mask 20.For example, Z1, Z2, Z3 are respectively set as 30 minutes, 50 minutesand 60 minutes. The temperatures P1 and P2 are respectively set atnormal temperature (e.g., 25° C.) and 300° C.

In the first step, as shown in FIG. 9A, the sample 76 is heated suchthat its temperature is increased from the temperature P1 (25° C.) tothe temperature (300° C.) at a uniform speed (temperature increasespeed). Similarly, in the third step, the sample 76 is cooled such thatits temperature is decreased from the temperature P2 (300° C.) to thetemperature P1 (25° C.) at a uniform speed (temperature decrease speed).

FIG. 9B (a) is a plan view showing the sample 76 before it is subjectedto the heat treatment, and FIG. 9B (b) is a plan view showing the sample76 after it is subjected to the heat treatment. In FIGS. 9B (a) and 9B(b), a distance between the two points 76 a in the longitudinaldirection of the sample 76, i.e., in the longitudinal direction of theelongated metal 64, before the sample 76 is subjected to the heattreatment is shown by the symbol L1, and a distance therebetween afterthe sample 76 is subjected to the heat treatment is shown by the symbolL2. The two measurement points 76 a are set such that the distance L1 onthe sample 76 before it is subjected to the heat treatment is anappropriate distance for evaluation of a thermal recovery degree of eachsample 76, for example, about 500 mm. In FIGS. 9B (a) and 9B (b), thedifference between the distances L1 and L2 is overstated than in realityas a matter of convenience in explanation.

In FIGS. 9B (a) and 9B (b), the two measurement points 76 a are alignedalong the longitudinal direction of the sample 76. However, as long asthe thermal recovery of the sample 76 can be adequately observed, thearrangement of the measurement points 76 a is not specifically limited.

A method of marking the two measurement points 76 a is not specificallylimited. For example, the measurement points 76 a are marked asscratches formed in the sample 76.

Before the heat treatment, the distance L1 between the two measurementpoints 76 a in the longitudinal direction of the sample 76 is measured.In addition, after the heat treatment, the distance L2 therebetween ismeasured. Thereafter, a thermal recovery rate F of the sample 76 iscalculated based on the following expression.F={(L1−L2)/L1}10⁶ (unit: ppm)

The thermal recovery rate F is defined as parts per million of adifference between the distance L1 before the heat treatment and thedistance L2 after the heat treatment, relative to the distance L1between the two measurement points 76 a on the sample 76 before it issubjected to the heat treatment. For example, when L1 is 500 mm and L2is 499.995 mm, the thermal recovery rate F is +10 ppm. Measurements ofthe distances L1 and L2 are performed at a temperature of P1, i.e., at anormal temperature (25° C.).

The aforementioned elongated metal plate may have a corrugation that iscaused by the fact that an elongation percentage differs depending on aposition in the width direction during the rolling step. When there issuch a corrugation, the above-described lengths L1 and L2 may bedistances in consideration of the corrugation, which are obtained byscanning the surface of the sample 76 along the corrugation, or may bedistances without considering the corrugation. In either measuringmethod, the thermal recovery degree of the sample 73 can be evaluated.

For example, the below-described examples show results in which thedistances L1 and L2 on the sample 76 were measured with the use of anautomatic two-dimensional coordinate measuring machine AMIC-710manufactured by SINTO S-PRECISION, Ltd. In this case, the distances L1and L2 are distances on an X-Y coordinate without considering thecorrugation. The AMIC-710 machine includes a function of making constantan ambient temperature of an object to be measured, i.e., an ambienttemperature of the sample 76. Thus, the use of the AMIC-710 machineenables stable measurement unsusceptible to an ambient temperaturechange.

Thereafter, selection of an elongated metal plate 64 is carried outbased on a value of the obtained thermal recovery rate F. Herein, theselection of an elongated metal plate 64 is carried out in such a mannerthat only an elongated metal plate 64 that satisfies both the followingconditions (1) and (2) is used in the below-described manufacturingprocess of the deposition mask 20.

-   -   (1) An average value K1 of the thermal recovery rates F of the        respective samples 76 is not less than −10 ppm and not more than        +10 ppm.    -   (2) A dispersion K2 of the thermal recovery rates F of the        respective samples 76 is not more than 20 ppm.

The dispersion K2 of the thermal recovery rates F of the respectivesamples 76 is a value obtained by multiplying 3 to a standard deviationσ₁ of the thermal recovery rates F of the predetermined number ofsamples 76, e.g., forty samples 76. Namely, 3σ₁ is employed as thedispersion K2.

The above condition (1) means that the average value K1 of the thermalrecovery rates F of the respective samples 76 is sufficiently smallerthan the positional precision required for the through-holes 25 of thedeposition mask 20. Thus, by using the elongated metal plate 64satisfying the condition (1), it can be prevented that the dimension ofthe metal plate 21 constituting the deposition masks 20 is changedbecause of the thermal recovery in such a degree that the quality of thedeposition masks 20 is affected during the manufacturing process of thedeposition masks 20. Thus, it is not necessary to adjust, for each lot,positions of the through-holes 25 to be formed in the metal plate 21 inconsideration of the thermal recovery rate, and it is not necessary toadjust, for each lot, a tensing amount when the deposition masks 20 areattached to the frame in consideration of the thermal recovery rate.

The above condition (2) means that the dispersion K2 of the thermalrecovery rates F of the respective samples 76 is sufficiently smallerthan the positional precision required for the through-holes 25 of thedeposition mask 20. Thus, by using the elongated metal plate 64satisfying the condition (2), a dispersion of the positions of thethrough-holes 25 in a plurality of the deposition masks 20 obtained fromone elongated metal plate 64 can be made within an allowable range.Thus, it can be restrained that a position of the deposition material,which is deposited on the substrate by the deposition step using thedeposition masks 20 attached to the frame 15, varies in each individualdeposition mask. Therefore, when pixels of an organic EL display deviceis formed by deposition, the positional precision of pixels of theorganic EL display device can be improved. As a result, light emittingfrom each pixel can be taken out without any loss. Namely, a lightemission efficiency of each pixel can be enhanced.

Method of Manufacturing Deposition Mask

Next, a method of manufacturing the deposition mask 20 by use of theelongated metal plate 64 selected as described above is described withreference to FIGS. 10 to 19. In the below-described method ofmanufacturing the deposition mask 20, as shown in FIG. 10, the elongatedmetal plate 64 is supplied, the through-holes 25 are formed in theelongated metal plate 64, and the elongated metal plate 64 are severedso that the deposition masks 20 each of which is formed of thesheet-like metal plate 21 are obtained.

To be more specific, the method of manufacturing a deposition mask 20includes a step of supplying an elongated metal plate 64 that extendslike a strip, a step of etching the elongated metal plate 64 using thephotolithographic technique to form a first recess 30 in the elongatedmetal plate 64 from the side of a first surface 64 a, and a step ofetching the elongated metal plate 64 using the photolithographictechnique to form a second recess 35 in the elongated metal plate 64from the side of a second surface 64 b. When the first recess 30 and thesecond recess 35, which are formed in the elongated metal plate 64,communicate with each other, the through-hole 25 is made in theelongated metal plate 64. In the example shown in FIG. 11, the step offorming the second recess 35 is performed before the step of forming thefirst recess. In addition, between the step of forming the second recess35 and the step of forming the first recess 30, there is furtherprovided a step of sealing the thus made second recess 35. Details ofthe respective steps are described below.

FIG. 10 shows a manufacturing apparatus 60 for making the depositionmasks 20. As shown in FIG. 10, the winding body 62 having the core 61around which the elongated metal plate 64 is wound is firstly prepared.By rotating the core 61 to unwind the winding body 62, the elongatedmetal plate 64 extending like a strip is supplied as shown in FIG. 10.After the through-holes 25 are formed in the elongated metal plate 64,the elongated metal plate 64 provides the sheet-like metal plate 21 andfurther the deposition masks 20.

The supplied elongated metal plate 64 is transported by the transportrollers 72 to an etching apparatus (etching means) 70. The respectiveprocesses shown in FIGS. 11 to 19 are performed by means of the etchingmeans 70. In this embodiment, pluralities of the deposition masks 20 areassigned in the width direction of the elongated metal plate 64. Namely,the deposition masks 20 are made from an area occupying a predeterminedposition of the elongated metal plate 64 in the longitudinal direction.In this case, if the thermal recovery rate varies in the width directionof the elongated metal plate 64, the lengths of the deposition masks 20to be obtained and below-described total pitches also vary.

As shown in FIG. 11, a negative-type photosensitive resist material isfirstly applied to the first surface 64 a (lower surface in the sheetplane of FIG. 11) and the second surface 64 b of the elongated metalplate 64, so that resist films 65 c and 65 d are formed on the elongatedmetal plate 64.

Then, exposure masks 85 a and 85 b which do not allow light to transmitthrough areas to be removed of the resist films 65 c and 65 d areprepared. As shown in FIG. 12, the masks 85 a and 85 d are located onthe resist films 65 c and 65 d. For example, glass dry plates which donot allow light to transmit through the areas to be removed from theresist films 65 c and 65 d are used as the exposure masks 85 a and 85 d.Thereafter, the exposure masks 85 a and 85 b are sufficiently broughtinto tight contact with the resist films 65 c and 65 d by vacuumbonding.

A positive-type photosensitive resist material may be used. In thiscase, there is used an exposure mask which allows light to transmitthrough an area to be removed of the resist film.

After that, the resist films 65 c and 65 d are exposed through theexposure masks 85 a and 85 b. Then, the resist films 65 c and 65 d aredeveloped (developing step) in order to form an image on the exposedresist films 65 c and 65 d. Thus, as shown in FIG. 13, a resist pattern(also referred to simply as resist) 65 a can be formed on the firstsurface 64 a of the elongated metal plate 64, while a resist pattern(also referred to simply as resist) 65 b can be formed on the secondsurface 64 b of the elongated metal plate 64. The developing step mayinclude a resist heat treatment step of increasing a hardness of theresist films 65 c and 65 d. In the resist heat treatment step, theresist films are heated at a temperature of 300° C. for 5 minutes.

Then, as shown in FIG. 14, by using an etching liquid (e.g., ferricchloride solution), the elongated metal plate 64 is etched from the sideof the second surface 64 b, with the resist pattern 65 d formed on theelongated metal plate 64 serving as a mask. For example, the etchingliquid is ejected from a nozzle, which is disposed on the side facingthe second surface 64 b of the transported elongated metal plate 64,toward the second surface 64 b of the elongated metal plate 64 throughthe resist pattern 65 b. As a result, as shown in FIG. 14, areas of theelongated metal plate 64, which are not covered with the resist pattern65 b, are eroded by the etching liquid. Thus, a lot of second recesses35 are formed in the elongated metal plate 64 from the side of thesecond surface 64 b.

After that, as shown in FIG. 15, the formed second recesses 35 arecoated with a resin 69 resistant to the etching liquid. Namely, thesecond recesses 35 are sealed by the resin 69 resistant to the etchingliquid. In the example shown in FIG. 15, a film of the resin 69 isformed to cover not only the formed second recesses 35 but also thesecond surface 64 b (resist pattern 65 b).

Then, as shown in FIG. 16, the elongated metal plate 64 is subjected tothe second etching process. In the second etching process, the elongatedmetal plate 64 is etched only from the side of the first surface 64 a,so that the first recess 30 is gradually formed from the side of thefirst surface 64 a. This is because the elongated metal plate 64 iscoated with the resin 69 resistant to the etching liquid, on the side ofthe second surface 64 b. Thus, there is no possibility that the secondrecesses 35, which have been formed to have a desired shape by the firstetching process, are impaired.

The erosion by the etching process takes place in an area of theelongated metal plate 64, which is in contact with the etching liquid.Thus, the erosion develops not only in the normal direction (thicknessdirection) of the elongated metal plate 64 but also in a direction alongthe plate plane of the elongated metal plate 64. Thus, as shown in FIG.17, with the development of etching in the normal direction of theelongated metal plate 64, not only the first recess 30 becomescontinuous with the second recess 35, but also two first recesses 30,which are formed at positions facing two adjacent holes 66 a of theresist pattern 65 a, are merged with each other on a reverse side of abridge portion 67 a positioned between the two holes 66 a.

As shown in FIG. 18, the etching from the side of the first surface 64 aof the elongated metal plate 64 further develops. As shown in FIG. 18, amerged portion 43 where the two adjacent first recesses 30 are mergedwith each other is separated from the resist pattern 65 a, and theerosion by the etching process develops also in the normal direction(thickness direction) of the metal plate 64 at the merged portion 43below the resist pattern 65 a. Thus, the merged portion 43, which issharpened toward the one side along the normal direction of thedeposition mask, is etched from the one side along the normal directionof the deposition mask, so that the merged portion 43 is chamfered asshown in FIG. 18. Thus, the inclination angle θ1, which is defined bythe wall surface 31 of the first recess 30 with respect to the normaldirection of the deposition mask, can be increased.

In this manner, the erosion of the first surface 64 a of the elongatedmetal plate 64 by the etching process develops in the whole area formingthe effective area 22 of the elongated metal plate 64. Thus, a maximumthickness Ta along the normal direction of the elongated metal plate 64,in the area forming the effective area 22, becomes smaller than amaximum thickness Tb of the elongated metal plate 64 before beingetched.

When the etching process from the side of the first surface 64 a of theelongated metal plate 64 develops by a preset amount, the second etchingprocess to the elongated metal plate 64 is ended. At this time, thefirst recess 30 extends in the thickness direction of the elongatedmetal plate 64 up to a position where it reaches the second recess 35,whereby the through-hole 25 is formed in the elongated metal plate 64 bymeans of the first recess 30 and the second recess 35 that are incommunication with each other.

After that, as shown in FIG. 19, the resin 69 is removed from theelongated metal plate 64. For example, the resin 69 can be removed byusing an alkali-based peeling liquid. When the alkali-based peelingliquid is used, as shown in FIG. 19, the resist patterns 65 a and 65 bare removed simultaneously with the removal of the resin 69. However,after the removal of the resin 69, the resist patterns 65 a and 65 b maybe removed separately from the resin 69.

The elongated metal plate 64 having a lot of through-holes 25 formedtherein is transported to a cutting apparatus (cutting means) 73 by thetransport rollers 72, 72 which are rotated while sandwichingtherebetween the elongated metal plate 64. The above-described supplycore 61 is rotated through a tension (tensile stress) that is applied bythe rotation of the transport rollers 72, 72 to the elongated metalplate 64, so that the elongated metal plate 64 is supplied from thewinding body 62.

Thereafter, the elongated metal plate 64 in which a lot of recesses 30,35 are formed is cut by the cutting apparatus (cutting means) 73 to havea predetermined length and a predetermined width, whereby the sheet-likemetal plate 21 having a lot of through-holes 25 can be obtained.

In this manner, the deposition mask 20 formed of the metal plate 21having a lot of through-holes 25 can be obtained. According to thisembodiment, the first surface 21 a of the metal plate 21 is etched overthe whole effective area 22. Thus, the thickness of the effective area22 of the deposition mask 20 can be reduced, and the outline of theportion 43, where the distal edges 32 of the wall surfaces 31 of the twofirst recesses 30 formed on the side of the first surface 21 a aremerged with each other, can have a chamfered shape. As a result, theaforementioned angle θ1 can be increased, to thereby improve theutilization efficiency of the deposition material and the positionalprecision of deposition.

In addition, according to this embodiment, since the above conditions(1) and (2) are satisfied, there is used the elongated metal plate 64 inwhich the average value and the dispersion of the thermal recovery ratesmeasured at the respective positions in the width direction D2 arerestrained. Therefore, it can be restrained that the positions of thethrough-holes 25 of a plurality of the deposition masks 20 obtained fromthe elongated metal plate 64 vary in each individual deposition mask.

Deposition Method

Next, a method of depositing the deposition material onto the substrate92 by use of the obtained deposition mask 20 is described. As shown inFIG. 2, the deposition mask 20 is firstly brought into tight contactwith the substrate 92. At this time, as shown in FIG. 1, the depositionmasks 20 are attached to the frame 15 in a tensed state, so that thesurface of each deposition mask 20 is in parallel with the surface ofthe substrate 92. According to this embodiment, there is used theelongated metal plate 64 that is selected beforehand based on theaverage value and the dispersion of the thermal recovery rates in thewidth direction of the elongated metal plate 64. Thus, as compared witha case in which such selection is not carried out, it can be restrainedthat the length of each deposition mask 20 differs from a designedvalue, and that lengths of a plurality of the masks 20 vary from oneanother. Thus, a deviation of the positions of the through-holes 25 ofeach deposition mask 20 with respect to the frame 15 from the designedvalue can be reduced. Therefore, the deposition material can bedeposited onto the substrate 92 with high positional precision.Therefore, when pixels of an organic EL display device are formed bydeposition, the dimensional precision and the positional precision ofthe pixels in the organic EL display device can be improved. As aresult, light emitting from each pixel can be taken out without anyloss. Namely, a light emission efficiency of each pixel can be enhanced.

In this embodiment, there is explained the example in which the firstsurface 21 a of the metal plate 21 is etched over the whole effectivearea 22. However, not limited thereto, the first surface 21 a of themetal plate 21 may be etched over only a part of the effective area 22.

In addition, in this embodiment, there is explained the example in whicha plurality of the deposition mask 20 are assigned in the widthdirection of the elongated metal plate 64. In addition, there isexplained the example in which a plurality of the deposition masks 20are attached to the frame 15 in the deposition step. However, thepresent invention is not limited thereto. As shown in FIG. 20, adeposition mask 20 having a plurality of the effective areas 22, whichare arranged like a grid along both the width direction and thelongitudinal direction of the metal plate 21, may be used. Also in thiscase, by using the elongated metal plate 64 having the reduceddispersion of the thermal recovery rates in the width direction, it canbe restrained that a degree of dimensional change caused by heat variesdepending on a position in the width direction of the deposition mask20. Therefore, the positional precision of the deposition material to bedeposited onto the substrate can be improved.

EXAMPLES

Next, although the present invention is described in more detailreferring to examples, the present invention is not limited to the belowexamples as long as it departs from the scope of the present invention.

First Winding Body and First Sample

Firstly, by performing the aforementioned rolling step, the slittingstep, the annealing step and the cutting step were performed to the basemetal made of the invar alloy, a winding body (first winding body)around which an elongated metal plate was wound was manufactured.

To be specific, a first rolling step, in which a first hot rolling stepand a first cold rolling step were performed in this order, was firstlyperformed. Then, a first slitting step, in which both ends in the widthdirection of the elongated metal plate were slit over a range of notless than 3 mm and not more than 5 mm, respectively, was performed.Thereafter, a first annealing step, in which the elongated metal platewas continuously annealed at 500° C. for 60 seconds, was performed.Further, a second rolling step including a second cold rolling step wasperformed to the elongated metal plate having underwent the firstannealing step. Then, a second slitting step, in which both ends in thewidth direction of the elongated metal plate were slit over a range ofnot less than 3 and not more than 5 mm, respectively, was performed.Thereafter, a second annealing step, in which the elongated metal platewas continuously annealed at 500° C. for 60 seconds, was performed.Thus, the elongated metal plate 64 of about 600 mm in width, which has adesired thickness, was obtained. After that, a cutting step, in whichboth ends in the width direction of the elongated metal plate 64 werecut over a predetermined range, respectively, was performed such thatthe width of the elongated metal plate 64 was finally adjusted to adesired width, specifically, 500-mm width.

In the above cold rolling step, a pressure adjustment with a backuproller was performed. Specifically, the shape and the pressure of thebackup roller of a rolling machine were adjusted such that the elongatedmetal plate 64 was bilaterally symmetric in shape. In addition, the coldrolling step was performed while being cooled with rolling oil such ascoal oil. After the cold rolling step, a cleaning step, in which theelongated metal plate was cleaned with a hydrocarbon cleaning agent, wasperformed. After the cleaning step, the slitting step was performed.

After that, by cutting the elongated metal plate 64 along the widthdirection by means of a shearing cutter, a first sample metal plate madeof a metal plate having a width of 500 mm and a projection length of 700mm was obtained. Two first sample metal plates were cut out in theforward end of the elongated metal plate 64, and two first sample plateswere cut out in the rearward end of the elongated metal plate 64. The“projection length” means a length of the metal plate (dimension in therolling direction) when viewed from directly above, i.e., when acorrugation of the metal plate is discounted. The width of the firstsample metal plate means a distance between a pair of ends of the firstsample metal plate in the width direction. The pair of ends of the firstsample metal plate are ends that have been formed by the cutting step inwhich the both ends in the width direction of the metal plate obtainedby the rolling step and the annealing step, and extend substantiallylinearly.

Then, four first sample metal plates were divided equally into ten alongthe longitudinal direction. Thus, forty first samples in total eachhaving a width of 50 mm and a projection length of 700 mm were obtained.Thereafter, each first sample was scratched by means of a needle to markeach first sample with two measurement points. The two measurementpoints were made such that a gap of about 500 mm was defined between thetwo measurement points in the longitudinal direction.

Then, the respective first samples were subjected to the heat treatment.Before and after the heat treatment, the distances L1 and L2 between thetwo measurement points in the longitudinal direction of each firstsample were measured at a temperature of 25° C. In the heat treatment,the temperature of each first sample was increased from 25° C. to 300°C. for 30 minutes, then the temperature of each first sample was kept at300° C. for 5 minutes, and thereafter the temperature of each firstsample was decreased from 300° C. to 25° C. for 60 minutes. Herein, as ameasuring machine that applied the heat treatment to each first sampleand measured a distance between the two measurement points on each firstsample, the above-described automatic two-dimensional coordinatemeasuring machine AMIC-710 manufactured by SINTO S-PRECISION, Ltd wasused. In addition, the aforementioned thermal recovery rates F werecalculated based on the measured distances L1 and L2.

After the measurement, it was found that the average value K1 of thethermal recovery rates F of the respective first samples was −2 ppm, andthat the dispersion K2 of the thermal recovery rates was 16 ppm. Bycomparing these measurement results with the above conditions (1) and(2), it was found that the first sample satisfied both the conditions(1) and (2). Thus, it can be judged that the first winding body fromwhich the first samples were taken out can be used as a material formanufacturing deposition masks.

Evaluation of Primary Effect

A lot of deposition masks each having five effective areas along thelongitudinal direction were manufactured by using the elongated metalplate of the first winding body from which the above first samples wereobtained. The respective effective areas of each deposition mask areprovided with a number of through-holes in a regular arrangement. Then,in order to evaluate a positional precision of the obtained depositionmasks, total pitches of the respective depositions masks were measured,and an average value and a dispersion of the total pitches werecalculated.

Herein, the “total pitch” means a distance between predetermined twopoints on a deposition mask. The positions of the two points are notspecifically limited, as long as the positional precision of adeposition mask can be evaluated. Herein, a distance between apredetermined mark which is formed in the vicinity of the effective arealocated on one end side of the deposition mask, and a predetermined markwhich is formed in the vicinity of the effective area located on theother end side of the deposition mask, was measured as the total pitch.The total pitch in this case is about 600 mm in design.

Similarly to the case of the thermal recovery rate, a value obtained bymultiplying 3 to a standard deviation σ_(z) of measured values of thetotal pitches of the respective deposition masks, i.e., 3σ₂ was employedas a reference of a dispersion degree of the total pitches.

The average value of the measurement values of the total pitches of thedeposition masks obtained from the first winding body was 600.0018 mmand the dispersion (3σ₂) thereof was 9.3 μm. The number of measurementsfor the calculation of the standard deviation (σ₂) was set such that thevalue of the standard deviation (σ₂) has sufficient degree of certaintyfor comparison between the deposition masks obtained from the firstwinding body and the deposition masks obtained from a second windingbody to a tenth winding body described below. To be specific, the totalpitch was measured at two positions on each of the forty first samples,whereby the number of measurements was set eighty. Allowance ranges ofthe average value and the dispersion of the measurement values of thetotal pitches of the deposition masks can be determined in considerationof a pixel density of an organic EL display device to be manufactured byuse of the deposition masks. For example, when an organic EL displaydevice having a pixel density of 400 ppi, for example, it is requiredthat an average value of measurement values of total pitches of thedeposition masks is within a range of a designed value (e.g., 600.0000mm)±0.005 mm, and that a dispersion of the measurement values of thetotal pitches of the deposition masks is not more than 0.01 mm. Owing tothis setting, a total pitch of an obtained deposition mask can be withina range of a designed value (e.g., 600.0000 mm)±0.005 mm, i.e., withinan allowable range.

In addition, the total pitch of a deposition mask obtained from thefirst winding body was evaluated in terms of process capacity index. Theprocess capacity index is a numerical value of a quantity achievementcapacity of a process (process capacity). In general, when the processcapacity index is not less than 1.33, it can be said that the processhas a good quality achievement capacity.

Herebelow, a method of calculating the process capacity index isdescribed. A process capacity index in which an average value ofproperty values of an object to be manufactured as a result of a processcan be adjusted is calculated by the following expression.Cp=(USL−LSL)/(6×σ₂)

USL and LSL respectively represent an upper specification value and alower specification value. In this embodiment for example, as describedabove, since the allowance value of the total pitch is 600.0000 mm±0.015mm, USL is 600.015 mm and LSL is 599.985 mm. The phrase “an averagevalue of property values can be adjusted” means a case in which theaverage value of the property values can be made as an intermediatevalue between USL and LSL by adjustment of the process.

On the other hand, a process capacity index Cpk in which it isconsidered that the average value of the property values departs fromthe intermediate value between USL and LSL is calculated by thefollowing expression.Cpk=(1−k)×Cp

The symbol k is calculated by the following expression.

$k = \frac{{\frac{{USL} + {LSL}}{2} - \mu}}{\frac{{USL} - {LSL}}{2}}$

Herein, μ is an average value of the total pitches of the depositionmasks obtained from the first winding body.

In this example, the above Cpk is employed as the process capacityindex. The process capacity index Cpk of the total pitches of thedeposition masks obtained from the elongated metal plate of the firstwinding body was 1.42.

Evaluation of Secondary Effect

A deposition material was deposited on a substrate by using thedeposition masks manufactured from the elongated metal plate of thefirst winding body. A pattern of a lot of through-holes formed in theused deposition masks is a stripe pattern adapted to a pixel density of300 ppi. An organic luminescent material for green color emittinggreen-colored light was used as the deposition material. Thereafter,central coordinate positions of a plurality of green-colored luminescentlayers formed of the organic luminescent material for green color weremeasured. Measurement of the central coordinate positions was carriedout for nine green-colored luminescent layers out of a plurality of thegreen-colored luminescent layers formed based on one effective area of adeposition mask. Similarly to the above sample evaluation case, in theevaluation of ten deposition masks taken out from one elongated metalplate, if the number of effective areas present in one deposition maskis five, the number of green-colored luminescent layers to be measuredis 450(=10×5×9).

Deviation amounts from the designed value were calculated for therespective measured central coordinate positions. In addition, thestandard deviation σ₃ of the deviation amounts was calculated. Then, itwas judged whether the dispersion (3σ₃) of the deviation amounts was notmore than an allowable value or not. At this time, the allowable valueof the dispersion of the deviation amounts of the central coordinatepositions was 10 μm. The measurement showed that the dispersion of thedeviation amounts of the central coordinate positions was 8.7 μm.Namely, it was found that the positional precision of the depositionmaterial was good.

Second to Tenth Winding Bodies and Second to Tenth Samples

Similarly to the first winding body, a second winding body to a tenthwinding body were manufactured from a base metal formed of an invaralloy. Further, as to the second winding bodies to the tenth windingbody, measurement of the thermal recovery rates of the samples taken outfrom the respective winding bodies, as well as the above evaluation ofprimary effect and the evaluation of secondary effect related to thedeposition masks manufactured from the elongated metal plates of therespective winding bodies were carried out in the same manner by whichthe measurement and evaluation of the first winding body were carriedout.

Summary of Judgment Results of Respective Samples

FIG. 21 shows measurement results of the thermal recovery rates of therespective samples taken out from the first winding body to the tenthwinding body. As shown in FIG. 21, judgment results of the first,second, third and fifth samples were “acceptable”. Namely, both of theconditions (1) and (2) were satisfied. On the other hand, judgmentresults of the fourth, sixth, seventh, eighth, ninth and tenth sampleswere “unacceptable”. Namely, at least one of the above conditions (1)and (2) was not satisfied. To be specific, the above condition (1) wasnot satisfied in the seventh, eighth and ninth samples. The abovecondition (2) was not satisfied in the fourth and sixth samples. Neitherthe condition (1) nor the condition (2) was satisfied in the tenthsample.

Summary of Evaluation Results of Primary Effect and Secondary Effect

FIGS. 22 and 23 respectively show the evaluation results of the primaryeffect and the secondary effect related to the deposition masksmanufactured from the elongated metal plates of the first winding bodyto the tenth winding body.

As shown in FIGS. 22 and 23, as to the deposition masks manufactured bythe elongated metal plates obtained from the first, second, third andfifth winding bodies, both the judgment result of the primary effect andthe judgment result of the secondary effect were “acceptable”.Specifically, regarding the primary effect, as shown in FIG. 22, theaverage value of total pitches (TP) was within the range of 600.0000mm±0.005 mm, the dispersion of TP was not more than 0.01 mm, and theprocess capacity index Cpk was not less than 1.33. Regarding thesecondary effect, as shown in FIG. 23, the dispersion of the deviationamounts of the central coordinate positions of the manufacturedgreen-colored luminescent layers was not more than 10 μm.

On the other hand, as to the deposition masks manufactured by theelongated metal plates obtained from the fourth, sixth seventh, eighth,ninth and tenth winding bodies, both the judgment result of primaryeffect evaluation and the judgment result of secondary effect evaluationwere “unacceptable”. Specifically, regarding the primary effect, theprocess capacity index Cpk was less than 1.33. Regarding the secondaryeffect, the dispersion of the deviation amounts of the centralcoordinate positions of the manufactured green-colored luminescentlayers was greater than 10 μm. Further, as to the deposition masksmanufactured by using the elongated metal plates obtained from the sixthto tenth winding bodies, the average value of TP departed from the rangeof 600.0000 mm±0.005 mm. Regarding the deposition mask manufactured byusing the elongated metal plate obtained from the tenth winding body,the dispersion of TP was greater than 0.01 mm.

As can be understood from the comparison of FIGS. 21, 22 and 23, thejudgment result based on the above conditions (1) and (2) and thejudgment result based on the primary effect and the secondary effectcompletely coincide to each other. Namely, by utilizing the aboveconditions (1) and (2), it is possible to select an elongated metalplate 64 capable of improving the process capacity index of themanufacturing process of deposition masks, and of forming luminescentlayers with high positional precision. That is to say, the aboveconditions (1) and (2) are considered to be significantly influentialjudging method for selecting the elongated metal plate 64.

DESCRIPTION OF REFERENCE NUMERALS

-   20 Deposition mask-   21 Metal plate-   21 a First surface of metal plate-   21 b Second surface of metal plate-   22 Effective area-   23 Surrounding area-   25 Through-hole-   30 First recess-   31 Wall surface-   35 Second recess-   36 Wall surface-   55 Base metal-   56 Rolling apparatus-   57 Annealing apparatus-   61 Core-   62 Winding body-   64 Elongated metal plate-   64 a First surface of elongated metal plate-   64 b Second surface of elongated metal plate-   65 a, 65 b Resist pattern-   65 c, 65 d Resist film-   85 a, 85 b Exposure mask

The invention claimed is:
 1. A method of inspecting a metal plate to beused for manufacturing a deposition mask by forming a plurality ofthrough-holes in the metal plate, the method comprising: obtaining aplurality of samples from the metal plate; measuring a distance L1between two measurement points on each sample before a heat treatment;measuring a distance L2 between the two measurement points on eachsample after the heat treatment; a step of judging whether the followingconditions (1) and (2) are satisfied: (1) an average value of a thermalrecovery rates of the respective samples is not less than −10 ppm andnot more than +10 ppm; and (2) a dispersion of the thermal recoveryrates of the respective samples is not more than 20 ppm; wherein thethermal recovery rate F of each sample is defined by the followingexpression:F={(L1−L2)/L1}×10⁶ (ppm), wherein the samples are obtained by cutting atleast one sample metal plate, which is obtained by cutting the metalplate along a width direction of the metal plate, into two or moresamples along a longitudinal direction of the metal plate; wherein thetwo measurement points on each sample are aligned along the longitudinaldirection of the metal plate; wherein the heat treatment includes afirst step of increasing a temperature of each sample from 25° C. to300° C. for 30 minutes, a second step of keeping the temperature of eachsample at 300° C. for 5 minutes, and a third step of decreasing thetemperature of each sample from 300° C. to 25° C. for 60 minutes; andwherein the dispersion of the thermal recovery rates is a value obtainedby multiplying a standard deviation of the thermal recovery rates of therespective samples by a factor of
 3. 2. The method of inspecting a metalplate according to claim 1, wherein the metal plate includes an invaralloy.
 3. The method of inspecting a metal plate according to claim 1,wherein the thickness of the metal plate is not more than 0.100 mm.